Cypress Semiconductor FX2LP Información técnica Pagina 118

  • Descarga
  • Añadir a mis manuales
  • Imprimir
  • Pagina
    / 460
  • Tabla de contenidos
  • MARCADORES
  • Valorado. / 5. Basado en revisión del cliente
Vista de pagina 117
EZ-USB FX2 Technical Reference Manual
Page 5-6 EZ-USB FX2 Technical Reference Manual v2.1
On-chip FX2 memory consists of three RAM regions:
0x0000-0x1FFF (Main RAM)
0xE000-0xE1FF (Scratch RAM)
0xE200-0xFFFF (Registers/Buffers)
The 8K “Main RAM” occupies code-memory (PSEN) and data-memory (RD/WR) addresses
0x0000-0x1FFF.
The 512-byte “Scratch RAM” occupies data-memory (RD/WR) addresses 0xE000-0xE1FF.
7.5K of control/status registers and endpoint buffers occupy data-memory (RD/WR) addresses
0xE200-0xFFFF.
When off-chip memory is connected to the FX2, it fills in the gaps not occupied by on-chip FX2
RAM. Since the lower 8K of memory is occupied by on-chip program/data memory and the upper
8K is occupied by on-chip data memory, the off-chip memory cannot be active in these regions.
Nevertheless, it’s still safe to populate those regions with off-chip memory, as the following para-
graphs explain.
The middle column of Figure 5-2 indicates FX2 data memory (activated by the RD and WR
strobes) and the right-most column indicates FX2 code memory (activated by PSEN).
The “middle” 48K of the data-memory space may be filled with off-chip memory, since it does not
conflict with the upper and lower 8K of on-chip FX2 data memory. To allow a 64K RAM to be con-
nected to the FX2, the FX2 gates its RD and WR strobes to exclude the top and bottom 8K for off-
chip accesses. Therefore, a 64K RAM can be connected to FX2, and the top and bottom 8K of it
are automatically disabled.
Likewise, when a 64K code memory (PSEN strobe) is attached to the FX2 (when EA = 0), the
lower 8K is automatically excluded for off-chip code fetches, avoiding conflict with the on-chip
code memory inside FX2.
The asterisks in Figures 5-2 and 5-3 indicate memory regions that may be accessed using three
special FX2 resources:
Setup Data Pointer (see Section 8.7)
Upload or download via USB (see Section 3.8)
Code boot from an I²C-compatible EEPROM (see Section 13.5 and Section 3.4)
Vista de pagina 117
1 2 ... 113 114 115 116 117 118 119 120 121 122 123 ... 459 460

Comentarios a estos manuales

Sin comentarios